Light-emitting diode device

ABSTRACT

A LED device includes a substrate; a plurality of LED units on the substrate, wherein each LED unit includes: a first semiconductor layer; a second semiconductor layer; a first sidewall; a second sidewall opposite to the first sidewall; and a third sidewall connecting the first and second sidewalls; a first group of conductive connecting structure including n (n is an integer, and n&gt;1) first conductive connecting structures formed on the first sidewall of one of the LED units and electrically connecting the LED units; and a second group of conductive connecting structure including m (m is an integer, m≥1, and n≠m) second conductive connecting structures formed on the second sidewall of the same one of the LED unit and electrically connecting the LED units; wherein each of the first and the second conductive connecting structures includes a middle part, a first and a second extending parts; wherein the first and the second extending parts have different length.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 14/954,465, filed on Nov. 30, 2015, now U.S. Pat.No. 9,871,178, which is a divisional application of U.S. patentapplication Ser. No. 13/796,044, filed on Mar. 12, 2013, now U.S. Pat.No. 9,203,003, which claims the right of priority based on Taiwanesepatent application, Ser. No. 101108402, entitled “Light-Emitting DiodeDevice”, filed on Mar. 12, 2012, and the contents of which are herebyincorporated by reference in their entirety.

BACKGROUND 1. Technical Field

The present application relates to a light-emitting diode device and inparticular to a light-emitting diode device with high light extractionefficiency.

2. Description of the Related Art

Different from the conventional lighting, the emitting principles andstructures of light-emitting diode devices (LEDs) have advantages suchas low power consumption, long operational life, without warming-time,quick response, small volume, shockproof and high productivity. LEDshave been widely used in applications and are easily to form small orarray devices, such as the optical display devices, laser diodes,traffic lights, data storage devices, communication devices and medicaldevices.

Referring to FIG. 1A and FIG. 1B, a conventional light-emitting diodedevice 1 comprises a transparent substrate 10, a plurality oflight-emitting diode units 12 extended two dimensionally and formedclose to each other on the transparent substrate 10. Each stack 120 ofthe light-emitting diode units 12 comprises a first semiconductor layer121, an active layer 122, and a second semiconductor layer 123. Becausethe transparent substrate 10 is not conductive, gaps 14 formed byetching between the light-emitting diode epitaxial stacks 120 caninsulate the light-emitting diode units 12 from each other. Next,partial exposed area is exposed by etching the light-emitting diodeepitaxial stacks 120 to the first semiconductor layer 121. Then, forminga conductive connecting structure 19 including a first electrode 18 anda second electrode 16 on the exposed area of the first semiconductorlayer 121 of the light-emitting diode epitaxial stack 120 and the secondsemiconductor layer 123 of adjacent light-emitting diode epitaxial stack120 respectively. The first electrode 18 and the second electrode 16respectively comprise a first electrode extension 180 and a secondelectrode extension 160 formed on the first semiconductor layer 121 ofthe light-emitting diode epitaxial stack 120 and the secondsemiconductor layer 123 of adjacent light-emitting diode epitaxial stack120 to help current spread evenly into the semiconductor layer. Theconductive connecting structure 19 selectively connects the secondsemiconductor layer 123 and the first semiconductor layer 121 ofadjacent light-emitting diode units 12 to form serial circuits orparallel circuits between the light-emitting diode units 12. There canbe air or an insulating layer 13 beneath the conductive connectingstructures 19 where in the insulating layer 13 is formed on the partialsurface of epitaxial stacks of the light-emitting diode unit 12 and thespace between the epitaxial stacks of adjacent light-emitting diode unit12 by CVD, PVD, sputtering and so on before forming the conductiveconnecting structures 19 to protect the epitaxial stacks and insulatethe adjacent light-emitting diode units. The material of the insulatinglayer 13 comprises Al₂O₃, SiO₂, AlN, SiN_(x), TiO₂, Ta₂O₅, or thecombination thereof.

However, when the conductive connecting structure 19 electricallyconnects the light-emitting diode units 12, because the depth of the gap14 between the light-emitting units 12 is large, it is easy to cause badconnection or broken line when forming conductive connecting structures19, and the yield of the devices is influenced therefore.

Furthermore, the light-emitting diode device 1 mentioned above canconnect to other devices to form a light-emitting apparatus. FIG. 2 is aschematic diagram illustrated the conventional light-emitting apparatus.As shown in FIG. 2, a light-emitting apparatus 100 comprises a sub-mount110 comprising a circuit 101, and the light-emitting diode device 1 isfixed onto the sub-mount 110; an electrical connection structure 104electrically connects a first electrode pad 16′ and a second electrodepad 18′ of the light-emitting diode device 1 and the circuit 101 of thesub-mount 110. The sub-mount 110 can be the lead frame or the largemounting substrate which is convenient for the circuit layout of thelight-emitting diode device 100 and suitable for heat dissipation. Theelectrical connection structure 104 can be the bonding wires or otherconnecting structures.

SUMMARY

The present application provides a light-emitting diode device,especially a light-emitting diode device with high light extractionefficiency.

An embodiment of the present application provides a light-emitting diodedevice including a substrate; a plurality of light-emitting diode unitsformed on the substrate, wherein each of the light-emitting diode unitsincludes: a first semiconductor layer; a second semiconductor layerformed on the first semiconductor layer; and a first sidewall, a secondsidewall opposite to the first sidewall and a third sidewall connectingthe first and second sidewalls; a first group of conductive connectingstructure electrically connecting the plurality of light-emitting diodeunits; and a second group of conductive connecting structureelectrically connecting the plurality of light-emitting diode units;wherein the first group of conductive connecting structure includes nfirst conductive connecting structures formed on the first sidewall ofone of the light-emitting diode units, wherein n is an integer, and n>1;wherein the second group of conductive connecting structure includes msecond conductive connecting structures formed on the second sidewall ofthe same one of the light-emitting diode unit; wherein m is an integer,m≥1, and n≠m; wherein the second conductive connecting structures arespatially separated from each other; wherein each of the first and thesecond conductive connecting structures includes a middle part, a firstextending part and a second extending part; wherein the first and thesecond extending parts of one of the first conductive connectingstructures have different length.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide easy understanding ofthe application, and are incorporated herein and constitute a part ofthis specification. The drawings illustrate the embodiments of theapplication and, together with the description, serve to illustrate theprinciples of the application.

FIG. 1A is a structure diagram showing the side view of a conventionalarray light-emitting diode device.

FIG. 1B is a structure diagram showing the top view of a conventionalarray light-emitting diode device.

FIG. 2 is a schematic diagram showing the structure of a conventionallight-emitting apparatus.

FIG. 3A is a structure diagram showing a sectional view of alight-emitting diode device in accordance with the first embodiment ofthe present application.

FIG. 3B is a structure diagram showing the top view of a light-emittingdiode device in accordance with the first embodiment of the presentapplication.

FIG. 4 is a diagram showing the partial plan view of the light-emittingdiode device in accordance with the first embodiment of the presentapplication.

FIG. 5 is a structure diagram showing the top view of thetwo-dimensional array light-emitting diode device in accordance with thesecond embodiment of the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following shows the description of the embodiments of the presentdisclosure in accordance with the drawings. With the Market demand, thesizes of light-emitting diode devices are miniaturized. When the area ofeach of the light-emitting diode units of the light-emitting diodedevice is miniaturized correspondingly. Opaque structures such aselectrodes formed on the light extraction surface of the light-emittingdiode unit, electrode extensions, and conductive connecting structuresaffect the light extraction efficiencies of the light-emitting diodeunits correspondingly.

First, FIG. 3A and FIG. 3B show the sectional view and top view of anarray light-emitting diode device 2 in accordance with the firstembodiment of the present application. Array light-emitting diode device2 has a substrate 20 having a first surface 201 and a bottom surface202, wherein the first surface 201 is opposite to the bottom surface202. The substrate 20 can be made of a single material, or can be thecomposite transparent substrate made of multiple materials. For example,the substrate 20 can be made of a first substrate and a second substratebonded to each other (not shown). In this embodiment, the material ofthe substrate 20 is sapphire. However, the material of the substrate 20can be LiAlO₂ (lithium aluminum oxide), ZnO (zinc oxide), GaP (galliumphosphide), Glass, Organic polymer sheet, AlN (aluminum nitride), GaAs(gallium arsenide), diamond, quartz, Si (silicon), SiC (siliconcarbide), and DLC (diamond like carbon). Then, a plurality of twodimensional extended arranged array light-emitting diode units 22 isformed on the first surface 201 of the substrate 20. The manufacturingprocess of the array light-emitting diode units 22 is described below:

First, an epitaxial stack is formed on the growth substrate (not shown)by a conventional epitaxial growth process and comprises a firstsemiconductor layer 221, an active layer 222, and a second semiconductorlayer 223. The material of the growth substrate can be GaAs, Ge(germanium), InP (indium phosphide), sapphire, SiC (silicon carbide),silicon, LiAlO₂ (lithium aluminum oxide), ZnO (zinc oxide), GaN (galliumnitride), and MN (aluminum nitride).

Then, as shown in FIG. 3B, a part of the epitaxial stacks is selectivelyremoved by photolithography process technology to form a plurality ofseparated light-emitting diode epitaxial stacks 220 on the substrate.Furthermore, an exposed area is formed on the first semiconductor layer221 of each light-emitting diode unit by the photolithography processtechnology as a platform for forming the following conductive connectingstructures.

In order to increase the light extraction efficiency of the device, thelight-emitting diode epitaxial stacks 220 can be disposed on thesubstrate 20 by substrate transferring and substrate bonding technology.The light-emitting diode epitaxial stacks 220 can be bonded to thesubstrate 20 directly by heating or pressure, or bonded to substrate 20by a transparent adhesive layer (not shown), wherein the material of thetransparent adhesive layer can be organic polymer transparent plastic,such as polyimide, BCB, PFCB, epoxy, acrylic resin, PET, and PC or thecombinations, a transparent conductive oxide metal layer, such as ITO,InO, SnO₂, FTO, ATO, CTO, AZO, and GZO or the combination thereof, or aninorganic insulating layer, such as Al₂O₃, SiN_(x), SiO₂, MN, TiO₂, andTa₂O₅ (Tantalum Pentoxide) or the combination thereof.

In fact, people with ordinary skill in the art can easily understandthat the method of arranging the light-emitting diode epitaxial stacks220 on the substrate 20 is not limited to the above. Depending ondifferent growing characteristics, the light-emitting diode epitaxialstacks 220 can be formed on the substrate 20 directly by epitaxialgrowth. Furthermore, according to different transferring times of thesubstrate 20, the structure which has a second semiconductor layer 223adjacent to the first surface 201 of the substrate 20, the firstsemiconductor layer 221 on the second semiconductor layer 223, and theactive layer 222 between the first semiconductor layer 221 and thesecond semiconductor layer 223 can be formed.

Then, an insulating layer 23 is formed on the partial surface of thelight-emitting diode epitaxial stacks 220 and the space between thelight-emitting diode epitaxial stacks 220 by CVD, PVD, or sputtering.The insulating layer 23 can protect the epitaxial stacks and insulatethe adjacent light-emitting diode units 22. The material of theinsulating layer 23 can be Al₂O₃, SiO₂, MN, SiN_(x), TiO₂, and Ta₂O₅ orthe combination thereof.

Thereafter, forming respectively a plurality of conductive connectingstructures 29 spatially separated from each other on the surface of thefirst semiconductor layer 221 and the surface of the secondsemiconductor layer 223 of the adjacent light-emitting diode units bysputtering. The conductive connecting structures 29 are spatiallyseparated from each other and extended along one direction (without anyelectrodes extending toward other directions) on the first semiconductorlayer 221, and are directly contacted with the first semiconductor layer221 such that the conductive connecting structures 29 electricallyconnected with each other through the first semiconductor layer 221.These spatially separated conductive connecting structures 29 furtherextend to the second semiconductor layer 223 of the other adjacentlight-emitting diode unit 22 for the other end to directly contact thesecond semiconductor layer 223 of the light-emitting diode unit 22 sothe adjacent two light-emitting diode units are connected in series.

In fact, people with ordinary skill in the art can easily understandthat the methods to electrically connect two adjacent light-emittingdiodes are not limited to the above. By arranging the two ends of theconductive connecting structures on the same or different polarities ofsemiconductor layers of different light-emitting diode units, thelight-emitting diode units can connect in series or in parallel by theconductive connecting structures.

Referring to FIG. 3B, in a serial circuit formed by a serially connectedarray light-emitting diode device 2, a first electrode pad 26 and asecond electrode pad 28 are respectively formed on the firstsemiconductor layer 221 and the second semiconductor layer 222 of thetwo light-emitting diode units 22 on the ends of the serial circuit. Thetwo electrode pads can connect electrically with external power sourceor other circuit devices by wiring or soldering. Furthermore, theelectrodes 26, 28 can be formed with the conductive connecting structure29 can be in one single process, or can be accomplished by multipleprocesses. The material of the electrode pads 26, 28 can be the same asor different from the material of the conductive connecting structure29.

Furthermore, to achieve a certain level of conductivity, the material ofthe conductive connecting structures 29 can be metal such as Au, Ag, Cu,Al, Pt, Ni, Ti, Sn, the alloy or the combination thereof.

Besides the first semiconductor layer 221 and the second semiconductorlayer 222, one layer or several same or different semiconductor layerscan be formed between the substrate 20 and the second semiconductorlayer 223 based on the requirement of different functions andcharacteristics. For example, a buffer layer can be formed between thesubstrate 20 and the first semiconductor layer 221 as a stress releaselayer to release the stress generated during epitaxial process.Furthermore, the second semiconductor layer 223 can be a transparentmetal oxide layer formed on the active layer 222, and one layer 224 ormultiple layers can be formed between the second semiconductor layer 223and the active layer 222. Because the transparent metal oxide layer hasbetter lateral current spreading performance, it can help to spread thecurrent evenly into the beneath semiconductor layers. Generally, thebandgap of the transparent metal oxide layer varies from 0.5 eV to 5 eVaccording to dopant types and formation processes so the transparentmetal oxide layer is considered as semiconductor structure. In theembodiment, the transparent metal oxide layer is ITO with a bandgapbetween 3.2 eV to 4.2 eV and is a semiconductor structure. The materialof the transparent oxide metal layer can also be ZnO, InO, SnO₂, FTO,ATO, CTO, AZO, GZO, and the combination thereof.

Since these conductive connecting structures 29 are arranged on thesemiconductor layers in one direction, there is no redundant electrodeextensions and electrodes. Comparing with the conventionallight-emitting diode units, the percentage of the light shading area ofthe light-emitting diode units 22 is reduced and the light extractionefficiency is increased.

According to the experimental results, the distance of lateral currentspreading of the metal conductive connecting structure on the surface ofthe light-emitting diode unit is limited to about 100 microns (μm).Therefore, in order to spread the current in the semiconductor layerevenly, it is necessary to adjust the arrangements of the conductiveconnecting structures on the semiconductor layers of the light-emittingdiode units. In addition, the shape of the light-emitting diode unitscan be changed to adjust the current spreading efficiency between thelight-emitting diode units.

FIG. 4 shows two of the light-emitting diode units of the light-emittingdiode device 2 in serial connection. In order to achieve the uniformcurrent spreading, a plurality of the conductive connecting structures29 is disposed on the horizontal sidewall 27 of the light-emitting diodeunit 22. The horizontal spacing D of every conductive connectingstructure is less than 100 microns. In other words, when the length ofthe horizontal sidewall is a micron, at least (a/100)−1 conductiveconnecting structures are disposed on the horizontal sidewall 27. In theembodiment, the length of the horizontal sidewall 27 is about 240microns. In order to make the horizontal spacing between conductiveconnecting structures 29 on the horizontal sidewall 27 less than 100microns, the number of the conductive connecting structures 29 is morethan (240/100)−1=1.4. As described in this embodiment, 2 or 3 conductiveconnecting structures are disposed on the one horizontal sidewall 27. Onthe vertical sidewall 25, because there is no conductive connectingstructures and the electrode extension which can help the currentspreading, to keep the spacing between conductive connecting structuresless than 100 microns, the length of the vertical sidewall is designedto be less than 150 microns. Each light-emitting diode unit has a firsthorizontal sidewall and a second horizontal sidewall opposite to thefirst horizontal sidewall. In order to spread the current more evenly,the conductive connecting structures 29 can be interlaced on the twohorizontal sidewalls. In this embodiment, the conductive connectingstructures arranged on the first horizontal sidewall, the secondhorizontal sidewall, the first horizontal sidewall, the secondhorizontal sidewall, and the first horizontal sidewall form the leftside to the right side, wherein the first horizontal sidewall has 3conductive connecting structures, and the second horizontal sidewall has2 conductive connecting structures.

In fact, people with ordinary skill in the art can easily understandthat the method of arranging the conductive connecting structures is notlimited to the above. The numbers and the positions of the conductiveconnecting structures arranged on the two sidewalls can be adjustedbased on different characteristics like extension direction and thelength of the sidewalls so the numbers of the conductive connectingstructures can be the same or different.

FIG. 5 shows the second embodiment in accordance with the presentapplication. The basic structure of the light-emitting diode device 3 issimilar with the light-emitting diode device 2 disclosed in the firstembodiment, and the similar code shows the similar structure in belowdescription. The light-emitting diode device 3 has a substrate 30 and aplurality of array light-emitting diode units 32 formed on the substrate30. A plurality of conductive connecting structures 39 is disposedseparately on each of the opposite sidewalls of the light-emitting diodeunits 32 according to the above rules above to electrically connect twoadjacent light-emitting diode units 32. On the two opposite ends or twoopposite sides of the substrate, the first electrode pad 36 and thesecond electrode pad 38 are disposed on the two adjacent light-emittingdiode units 32 of the two ends of the circuit to connect to thelight-emitting diode units electrically to the external power source andelectrical devices.

The foregoing description has been directed to the specific embodimentsof this invention. It will be apparent, however, that other alternativesand modifications may be made to the embodiments without escaping thespirit and scope of the application.

What is claimed is:
 1. A light-emitting diode device, comprising: asubstrate; a plurality of light-emitting diode units formed on thesubstrate, wherein each of the light-emitting diode units comprises: afirst semiconductor layer; a second semiconductor layer formed on thefirst semiconductor layer; and a first sidewall, a second sidewallopposite to the first sidewall and a third sidewall connecting the firstand second sidewalls; a first group of conductive connecting structureelectrically connecting the plurality of light-emitting diode units; anda second group of conductive connecting structure electricallyconnecting the plurality of light-emitting diode units; wherein thefirst group of conductive connecting structure comprises n firstconductive connecting structures formed on the first sidewall of one ofthe light-emitting diode units, wherein n is an integer, and n>1;wherein the second group of conductive connecting structure comprises msecond conductive connecting structures formed on the second sidewall ofthe same one of the light-emitting diode unit; wherein m is an integer,m≥1, and n≠m; wherein the second conductive connecting structures arespatially separated from each other; wherein each of the first and thesecond conductive connecting structures comprises a middle part, a firstextending part and a second extending part; wherein the first and thesecond extending parts of one of the first conductive connectingstructures have different length.
 2. The light-emitting diode device ofclaim 1, wherein the first extending parts of the first conductiveconnecting structures are arranged on and connected with the secondsemiconductor layer of the same one of the plurality of light-emittingdiode units, and the second extending parts of the first conductiveconnecting structures are arranged on and connected with one of thefirst and second semiconductor layers of an adjacent light-emittingdiode unit of the plurality of light-emitting diode units.
 3. Thelight-emitting diode device of claim 1, wherein a distance between twoadjacent first conductive connecting structures arranged on the samefirst sidewall is less than 100 microns.
 4. The light-emitting diodedevice of claim 1, wherein the first and the second extending partsextend from the middle part; and wherein a width of the middle part iswider than a width of the first extending part and/or the secondextending part.
 5. The light-emitting diode device of claim 1, whereinthe first sidewall has a length of A microns, wherein A is a real numberand larger than 100, and n is an integer larger than (A/100)−1.
 6. Thelight-emitting diode device of claim 1, wherein each one of the firstconductive connecting structures and each one of the second conductiveconnecting structures are arranged alternately.
 7. The light-emittingdiode device of claim 1, wherein the first and the second conductiveconnecting structures are not arranged on the third sidewall.
 8. Thelight-emitting diode device of claim 1, wherein a length of one of thethird sidewalls is less than 150 microns.
 9. The light-emitting diodedevice of claim 1, wherein each two of the first conductive connectingstructures next to each other on the same one of the plurality oflight-emitting diode units are arranged with an interval, and theintervals are equal.
 10. The light-emitting diode device of claim 1,further comprising: a pad formed on the first semiconductor layer ofanother one of the plurality of light-emitting diode units; and a thirdextending part, extending from the pad and arranged along one of thefirst and the second sidewalls of the another one of the plurality oflight-emitting diode units.
 11. The light-emitting diode device of claim1, wherein the first semiconductor layer and the second semiconductorlayer have different conductivity types.
 12. The light-emitting diodedevice of claim 2, wherein the second extending parts of the firstconductive connecting structures, which are arranged on and connectedwith the first semiconductor layer of the adjacent light-emitting diodeunit, extend in one direction.
 13. The light-emitting diode device ofclaim 1, wherein the second semiconductor layer comprises a transparentoxide metal layer and the first extending parts of the first conductiveconnecting structures contact the transparent oxide metal layer.
 14. Thelight-emitting diode device of claim 2, wherein the second extendingparts of the first conductive connecting structures are connected withone of the first and second semiconductor layers of the adjacentlight-emitting diode unit.
 15. The light-emitting diode device of claim1, wherein the first sidewalls are longer than the third sidewalls